1. Field of the Invention
This invention concerns a novel silicon-containing polymer. More specifically, it relates to a silicon-containing polymer useful for electronic materials having excellent performances such as high heat resistance, film-forming properties and transparency.
2. Description of the Prior Art
Silica, polyimide and the like have hitherto been employed as heat-resistant insulating materials in the field of electronic materials but they are not always safisfactory in workability and performance. The present inventors have been aware of heat-resistant insulation oils mainly composed of polysiloxane and siloxane bond-containing polymers having heat resistant insulating performance similar to silica (SiO.sub.2). Referring to the properties of these polymers, however, the former is an oily or low melting material and can not easily be used as the solid heat resistant insulating material. On the other hand, the latter has to rely on a chemical vapor deposition (CVD) process for the formation of insulating films, which is carried out through gas phase reaction and, therefore, provides poor productivity.
The inventors are aware of ladder polymers containing siloxane bonds in order to solve the foregoing problems. It is known that the ladder polymer is one of the means for improving the solubility and heat resistance of polymers.
While a siloxane bond-containing ladder polymer having the general formula: ##STR4## has been reported as the siloxane ladder polymer (refer to Japanese Patent Laid-Open No. 49540/1981), since the polymer is difficult to synthesize and the coating film resulting therefrom tends to cause cracking, it has not yet been put to practical use.
A siloxane-containing ladder polymer having the general formula: ##STR5## has also been reported (U.S. Pat. No. 3,485,857), but it has a low molecular weight and thus readily causes cracking in the coated film.
The object of this invention is to overcome the foregoing defects in the silicon-containing ladder polymers in the prior art and provide a novel silicon-containing polymer having solvent solubility and exhibiting an excellent heat resistant insulating property and film-forming property.